Autoimmunity is basically a process where the body attacks itself. The immune system, which at birth recognized what was 'self' and that everything else was 'not self', starts… attacking 'self'. 'Self' is the tissues and muscles and organs that make-up the human body (your specific human body hence 'self'). There has been much debate over what triggers the initial attack on the body, but there are many convincing theories. They include pollution (your body has to fight this too, so with so many different compounds and chemicals around, it makes the body go haywire), genetics (a predisposition to getting an Autoimmune Disease because one of your family members has one), and a virus/infection. (the straw that broke the camel's back, as it were, the theory is that in having to fight a virus/infection the immune system is working but this last virus/infection pushes it over the edge and it can no longer identify 'self') A very convincing argument being made is that it is all three working together, but no one knows for sure. More testing is being done. .
Most diseases today are caused b autoimmune process. ( Full Answer )